1. Field of the Invention
The present invention relates to a storage device having a rotation driving unit for rotating a plurality of disk type of storage media each loaded on a coaxial basis on a center shaft, and a plurality of actuators for moving a head for picking up information from the storage media along the storage media in a radial direction of the storage media.
2. Description of the Related Art
As the storage device as mentioned above, there are known a magnetic disk unit and an optical disk unit. Here there will be described the magnetic disk unit by way of example.
Hitherto, according to the conventional magnetic disk unit, in many cases, a spindle motor (including a magnetic disk medium) is associated with an actuator on a one-to-one basis. Further, there is also known a magnetic disk unit in which a plurality of actuators are associated with one spindle motor to store or read a large volume of information into or from a medium, so that a processing speed of one magnetic disk unit is improved. However, according to such a type of magnetic disk unit as mentioned above, a plurality of actuators are disposed around the spindle motor. This arrangement needs a large occupation for the actuators and magnetic circuits and thus invites a larger device. Furthermore, there is considered an arrangement in which a plurality of actuators are rotatably moved on a coaxial basis (cf. for example, Japanese Patent Application Laid Open Gazette Sho. 58-23362, and Japanese Patent Application Laid Open Gazette Sho. 62-78783). However, according to such an arrangement, a plurality of actuators are simply superposed on a single rotary shaft, or there is provided a sub-base for integrating the actuators with the magnetic circuits. This is associated with a problem that it is difficult to provide a compactness of the device, and particularly very difficult to provide, for example, 3.5 inch disk factor (146 by 101.6 by 25.4 millimeters). According to the technologies proposed in the above-referenced documents, it is obliged to provide a large structure for the magnetic circuit. This involves an increment of the cost of the magnetic disk unit. Thus, it has to say that the technologies proposed in the above-referenced documents are for an especial device, but not for the general devices. Particularly, according to the magnetic disk unit in which actuators are laminated, there is a tendency that a frequency characteristic for enhancing a dynamic positioning performance of the actuators is degraded. Further, it often happens that a performance of moving and stopping a head for reading and writing information at a proper position is also degraded owing to a thermal distortion, a failure of accuracy in a size of a height direction, and the like.
Further, the above-mentioned magnetic disk unit having a plurality of actuators is associated with the following problems.
FIG. 1 is a schematic diagram of the conventional magnetic disk unit.
A magnetic disk 10 rotates on a center shaft 11 in a direction of an arrow A by a spindle motor (not illustrated).
The magnetic disk unit is provided with two actuators 20. Each of the actuators 20 rotates on a rotary shaft 21 so that a magnetic head 30 provided on the top of the actuator 20 is moved in a radial direction of the magnetic disk 10 along the magnetic disk 10. Each of the magnetic heads 30 records on the magnetic disk 10 information according to a signal transmitted from an associated signal recording/regenerating means 40, or picks up information recorded on the magnetic disk 10 and transmits the same to the associated signal recording/regenerating means 40.
The magnetic disk 10 stores therein information as to usual data to be read or written and in addition information as to a servo for a position control of the magnetic head 30 to the magnetic disk 10. The magnetic head 30 picks up from the magnetic disk 10 a signal representative of information recorded on the magnetic disk 10. Each of the signal recording/regenerating means 40 regenerates both the signals as to the data and the servo, which are picked up by the head 30 of the top of the associated actuator 20, and transmits the same to a associated signal processing means 50. Each of the signal processing means 50 processes the signals regenerated by the signal recording/regenerating means 40, and instructs an associated position control means 60 to perform a position control for the associated actuator 20 in accordance with a processing result of the servo signal. Each of the position control means 60 controls the operation of the associated actuator 20 in accordance with the instruction from the associated signal processing means 50 so that the head 30 of the top of the associated actuator 20 moves to a desired position onto the magnetic disk 10.
According to the magnetic disk unit shown in FIG. 1, each of the actuator 20 is provided with the magnetic heads 30 the number of which is the same as that of the recording surfaces of the magnetic disk 10 (when only one magnetic disk 10 is concerned, two surfaces of the front and the back, and when two magnetic disks 10 are concerned, four surfaces), wherein each of the magnetic heads 30 is placed against the associated recording surface. Thus, it is possible to simultaneously access the same recording surface of the magnetic disk 10 with total two magnetic heads 30 of the two actuator 20.
FIG. 2 is a schematic diagram of an alternative conventional magnetic disk unit.
According to this magnetic disk unit, two actuators 20 are disposed in such a state that the two actuators 20 are laminated in a perpendicular direction with respect to the surface of the magnetic disk 10. The two actuators 20 may rotate independently on the same rotary shaft 21. In case of the magnetic disk unit, the total number of the magnetic heads 30 is the same as that of recording surfaces of the magnetic disk 10 (when two magnetic disks 10 are disposed on a laminating basis, four recording surfaces, and when three magnetic disks 10 are concerned, six surfaces), and a plurality of magnetic heads 30 (here two heads) are loaded on a plurality of actuators 20 (here two heads), respectively. Accordingly, it is possible to access a recording surface of the magnetic disk 10 with the associated one magnetic head 30. On the other hand, according to this magnetic disk unit, since there are plurality of actuators, it is possible to enhance a degree of freedom in such a manner that while a magnetic disk 10 is accessed with one of the actuators, another actuator is moved for the purpose of the successive access, and thereby increasing an access speed.
In this manner, the scheme of providing a plurality of actuators makes it possible to increase an access speed. However, as shown in FIGS. 1 and 2, this scheme needs a plurality of systems of circuits for the signal processing and the servo control, so that a scale of the circuits is obliged to be enlarged and complicated. Thus, this scheme is associated with problems that it is disadvantageous in size, and the cost will be increased, too.
Those problems may be common to a storage device for the optical disk unit and the photomagnetic disk unit, but not restricted to the magnetic disk unit. Further, those problems may be common to a device for loading a read/write medium and also a device for loading a read-only medium.
In view of the foregoing, it is an object of the present invention to provide a storage device having a plurality of actuators, which has a structure suitable for a miniaturization.
To achieve the above-mentioned objects, the present invention provides a first storage device comprising:
a rotation driving unit for rotating a disk type of storage medium loaded on a center shaft;
two actuators each having a head for picking up information from the storage medium, each of said two actuators rotating on a common rotary shaft and moving the associated head along the storage medium in a radial direction of the storage medium; and
a voice coil motor for rotating said two actuators on the rotary shaft,
wherein said voice coil motor comprises:
a first magnet provided for said two actuators on a common basis; and
two coils provided for said two actuators, respectively, and
wherein said voice coil motor rotates said two actuators on the common rotary shaft independently of one another.
According to the first storage device of the present invention as mentioned above, the first magnet is provided for the two actuators on a common basis. This feature makes it possible to use only one a magnetic circuit for driving the two actuators and also to drive the two actuators independently of one another by the single magnetic circuit. Thus, according to the first storage device of the present invention as mentioned above, the number of magnets and yokes can be reduced, too and thereby contributing to a miniaturization of the storage device despite the provision of a plurality of actuators.
In the first storage device of the present invention as mentioned above, it is preferable that said first storage further comprises two yokes, which are associated with said two actuators, respectively, said two yokes being disposed at both sides between which said first magnet intervenes.
Further, in the first storage device of the present invention as mentioned above, it is preferable that said two coils are disposed at both sides between which said first magnet intervenes.
Further, in the first storage device of the present invention as mentioned above, it is preferable that said rotation driving unit rotates a plurality of disk type of storage media each loaded on a coaxial basis on the center shaft, and as the plurality of disk type of storage media, an odd number of pieces of storage media each storing information on both front and back is loaded, and as said two actuators, an even number of pieces of heads for picking up information stored in both surfaces of front and back of the storage medium on a sharing basis for each surface is disposed on said two actuators in such a manner that said even number of pieces of heads are divided into two equal parts on said two actuators.
This feature makes it possible that the two actuators have the same weight and the same inertia, and it is possible to drive the actuators by the same driving force using the same control constant and thereby providing a device structure excellent in balance.
Further, in the first storage device of the present invention as mentioned above, it is preferable that said voice coil motor has two second magnets disposed at positions adjacent to said two yokes between the respective said two yokes and said first magnet, respectively.
While the use of the second magnet may increase the number of parts, it is possible to suppress the eddy-current which will be generated on the associated yoke, and thus it is possible to reduce the time constant of a coil for supplying a driving force to each actuator, and thereby permitting a high speed operation.
Furthermore, in the first storage device of the present invention as mentioned above, it is preferable that said storage device further comprises a stopper for limiting a rotary range of said two actuators. The use of the stopper may prevent the actuators from being damaged or malfunctioning.
Here, while it is acceptable that the stopper is arranged separately from the first magnet and the two yokes, it is preferable that said stopper is formed together with said first magnet and said two yokes into a module in one united body.
Still further, in the first storage device of the present invention as mentioned above, it is preferable that said storage device further comprises a flexible substrate for transmitting signals picked up by the heads of said two actuators, said flexible substrate being common to all the heads.
According to the first storage device of the present invention as mentioned above, the two actuators have the common rotary shaft. This feature permits to use only one flexible substrate for transmitting signals picked up by the heads of said two actuators. Thus, this is advantageous in cost as compared with a case where individual wiring is performed on each actuator.
To achieve the above-mentioned objects, the present invention provides a second storage device comprising:
a rotation driving unit for rotating a disk type of storage medium loaded on a common center shaft, said storage medium being adapted for storing information as to both data and servo;
a plurality of laminated type of actuators each having a head for picking up signals representative of information stored in the storage medium, each of said plurality of laminated type of actuators operating in a predetermined operating direction so that the associated head is moved along the storage medium in a radial direction of the storage medium, said plurality of laminated type of actuators operating independently of one another;
a plurality of signal regenerating units each corresponding to an associated one of said plurality of actuators for regenerating signals of both the data and the servo picked up by the head of the associated actuator;
a position control unit provided for said plurality of actuators on a common basis for controlling positions of said plurality of actuators independently of one another; and
a signal processing unit provided for said plurality of actuators on a common basis for processing signals regenerated by said plurality of signal regenerating units and instructing said position control unit to control positions of said plurality of actuators in accordance with a processing result of a servo signal.
Each of the actuators performs not only picking up signals but also a plurality of processes, for example, a process for moving a head to a desired position on a storage medium, and a process for changeover of a head, which is to be operative to pick up signals, in the event that one actuator is provided with a plurality of heads. Therefore, it is possible to share the operation in such a manner that while a certain actuator picks up a signal, another actuator moves for the purpose of picking up the subsequent signal.
The second storage device of the present invention has been made taking the above-mentioned matter into account. In the second storage device, one signal processing unit (corresponding to signal processing means 50 in FIGS. 1 and 2) is provided for a plurality of actuators, and one position control unit (corresponding to position control means 60 in FIGS. 1 and 2) is provided to perform a position control for the plurality of actuators.
This feature makes it possible to simplify a circuit structure without substantially lowering the access speed of the storage device as compared with that of the conventional storage device shown in FIG. 2. Thus according to the second storage device of the present invention, it is advantageous in space and cost.
To achieve the above-mentioned objects, the present invention provides a third storage device comprising:
a rotation driving unit for rotating a disk type of storage medium loaded on a common center shaft, said storage medium being adapted for storing information as to both data and servo;
two laminated type of actuators each having a head for picking up signals representative of information stored in the storage medium, each of said two of laminated type of actuators operating in a predetermined operating direction so that the associated head is moved along the storage medium in a radial direction of the storage medium, said two laminated type of actuators operating independently of one another;
a data signal regenerating unit provided for said two actuators on a common basis for regenerating signals of data picked up by the heads of said two actuators;
a servo signal regenerating unit provided for said two actuators on a common basis for regenerating signals of servo picked up by the heads of said two actuators;
a signal selection unit provided for said two actuators on a common basis for assigning the signals of the data and the servo to the data signal regenerating unit and the servo signal regenerating unit, respectively;
a position control unit provided for said two actuators on a common basis for controlling positions of said two actuators independently of one another; and
a signal processing unit provided for said two actuators on a common basis for processing signals regenerated by said data signal regenerating unit and signals regenerated by said servo signal regenerating unit and instructing said position control unit to control positions of said two actuators in accordance with a processing result of a servo signal.
The third storage device of the present invention has been made on the basis of the similar concept to the second storage device, too. According to the third storage device, there is provided two actuators, and the structure corresponding to the signal processing unit of the second storage device is divided into the data signal regenerating unit for regenerating signals of data, and the servo signal regenerating unit for regenerating signals of servo, and further there is provided the signal selection unit. Avoiding generation of timing of simultaneously picking up data signals by the heads of the two actuators makes it possible to simultaneously perform a regeneration of the data signal by one of the two actuators and a servo of another actuator. Further, according to the third storage device of the present invention, it is possible to reduce the circuit scale.
Furthermore, according to the third storage device of the present invention, in a similar fashion to that of the second storage device, the signal processing unit and the position control unit are provided for the two actuators on a common basis. Therefore, according to the third storage device of the present invention, it is possible to further reduce the circuit scale, as compared with the second storage device, and thus it is advantageous in space and cost.
In the second and third storage devices as mentioned above, it is preferable that said rotation driving unit rotates a plurality of disk type of storage media each loaded on a coaxial basis on the center shaft, and as to each of the plurality of disk type of storage media, servo sectors storing servo information are arranged at positions varied with respect to a circumferential direction of an associated storage medium in accordance with said plurality of actuators.
This feature makes it possible to differentiate timings for picking up of servo signals by the respective actuators, and thereby performing the position control for the actuators in mutually different timings.
Further, in the second and third storage devices as mentioned above, it is preferable that in order to simultaneously perform a data pick up by one head of one actuator and a preparation for a subsequent data pick up by another actuator, data sectors of the plurality of storage media are alternately arranged on storage areas shared by the plurality of actuators, or alternatively the data sectors are circularly arranged.
This feature makes it possible, when one head of a certain one actuator (referred to as a first actuator) picks up the data signal, to move another actuator (referred to a second actuator) for the purpose of picking up the subsequent data signal, and further makes it possible, in the that the second actuator is provided with a plurality of heads, to perform a changeover for picking up of the data signal between the heads. Thus, according to the second and third storage devices as mentioned above, it is possible to implement a higher speed of access.
Further, in the second and third storage devices as mentioned above, it is preferable that said signal processing unit stores a plurality of commands to indicate positions of the plurality of actuators and has on each actuator a command queue to perform reordering of the commands as a need arises.
An adoption of the command queue on each actuator makes it possible to perform an optimum ordering of the command on each actuator, and thereby contributing to an improvement of the access speed.